Transcript How microbes feed

Elements of Microbial
Nutrition, Ecology and
Growth
Chapter 7
Microbial nutrition
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____________: process by which chemicals
(nutrients) are acquired from environment and
used by organism
________________________: must be
provided; can be in elemental or molecular
form
Elements needed for life ________________
Ca Fe Na Cl Mg and some others
Microbial nutrition
Nutrients
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____________– required in large quantities;
principal roles in cell structure & metabolism
• proteins, carbohydrates
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____________or trace elements – required
in small amounts; involved in enzyme
function & maintenance of protein structure
• manganese, zinc, nickel
Microbial nutrition
Nutrients
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____________nutrients– atom or molecule
that contains a combination of atoms other
than carbon and hydrogen
• metals and their salts (magnesium sulfate, ferric
nitrate, sodium phosphate), gases (oxygen, carbon
dioxide) and water
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____________nutrients- contain
____________and ____________atoms
and are usually the products of living things
• methane (CH4), carbohydrates, lipids, proteins,
and nucleic acids
Microbial nutrition
Microbial nutrition
Chemical composition of cytoplasm
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70% water
proteins
96% of cell is composed of 6 elements
• ____________
• ____________
• ____________
• ____________
• ____________
See Table 7.2 for E. coli
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Microbial nutrition
- 6 major elements
How do organisms obtain carbon?
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____________– an organism that must
obtain carbon in an organic form made by
other living organisms (proteins,
carbohydrates, lipids and nucleic acids)
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____________- an organism that uses CO2,
an inorganic gas as its carbon source
• not dependent on other living things
6 major elements
Nitrogen
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Main reservoir is nitrogen gas (N2)
79% of earth’s atmosphere is N2
Nitrogen is part of the structure of proteins, DNA,
RNA & ATP – these are the primary source of N
for heterotrophs
Some bacteria & algae use inorganic N nutrients
(NO3-, NO2-, or NH3)
Some bacteria can fix N2
Regardless of how N enters the cell, it must be
converted to NH3, the only form that can be
combined with carbon to synthesis amino acids,
etc.
6 major elements
Oxygen
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O2 makes up ______% of atmosphere
essential to metabolism of many organisms
major component of carbohydrates, lipids and
proteins
plays an important role in structural &
enzymatic functions of cell
component of inorganic salts (sulfates,
phosphates, nitrates) & water
6 major elements
Hydrogen
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major element in all organic compounds
& several inorganic ones (water, salts &
gases)
gases are produced & used by microbes
roles of hydrogen
• maintaining ________
• forming H bonds between molecules
• serving as the source of free energy in
oxidation-reduction reactions of respiration
6 major elements
Phosphorous
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main inorganic source is phosphate (PO4-3)
derived from phosphoric acid (H3PO4) found
in rocks & oceanic mineral deposits
key component of ____________, essential
to genetics
serves in energy transfers (ATP)
6 major elements
Sulfur
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widely distributed in environment; rocks,
sediments contain sulfate, sulfides,
hydrogen sulfide gas and sulfur
essential component of some vitamins and
the amino acids: methionine & cysteine
contributes to stability of proteins by
forming disulfide bonds
Important mineral ions
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Potassium
Sodium
Calcium
Magnesium
Iron
Growth factors
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organic compounds that cannot be
synthesized by an organism & must be
provided as a nutrient (essential
____________ nutrient)
• essential amino acids – 20 – obtained from
•
food
vitamins
How microbes feed
Nutritional type is based carbon and
energy sources
Example:
 ____________: use inorganic carbon
(CO2)
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• Photoautotrophs – make their own energy
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using light (“photo”)
Chemoautotrophs – Make their own energy
using chemicals rather than light
terminology
Prefixes
 Troph- food,
nourishment
 Auto- self
 Hetero- other
 Photo- light
 Sapro- rotten
 Halo- salt
 Thermo- heat
 Psychro- cold
 Aero- air (O2)
How microbes feed
Suffixes:
 -phile to love
 -obe to live
 -troph food
examples:
 Autotroph
 Chemoautotroph
 Halophile, thermophile
 Aerobe, saprobe
 Aerophile (aerophilic)
How microbes feed
Facultative vs. obligate
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____________– organism is able to
adapt to a wide range of metabolic
conditions – therefore it can facultatively
switch its niche, habitat, nutrition etc.
____________or strict – has a narrow
niche, habitat due to limitations in its
nutrition or metabolism. Microbe can
only grow under those conditions.
 PRINT FULL SIZE
How microbes feed
Carbon
source
Energy source
photoautotrophs
CO2
____________
chemoautotrophs
CO2
Simple inorganic
____________
photoheterotrophs
organic
____________
chemoheterotrophs
organic
Metabolizing
organic
____________
examples
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How microbes feed
____________–
• Photoautotrophs – photosynthesis
6CO2 + 12H2O + light energy  C6H12O6 + 6O2 + 6H2O
• Chemoautotrophs – methanogens
4H2 + CO2  CH4 + 2H2O
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____________
• Chemoheterotrophs
C6H12O6 + 6O2  6CO2 + 6H2O + energy
How microbes feed
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____________– decompose dead
organisms, recycle elements, release
enzymes to digest materials
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____________– utilize tissues and fluids of
a living host and cause harm
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parasites and saprobes can be facultative
(opportunistic pathogen) or obligate
How microbes feed
saprobes
• Cannot engulf large
particles of food
• Substrate is
digested
_________ by
secreted enzymes
• Small molecules
are transported into
cell
How microbes feed
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How microbes live
Symbiosis
Means “________________________”
 Organisms (____________) have close association
1. ____________=obligatory, both symbionts benefit
• Termite gut flagellates
2. ____________=commensal receives benefit,
symbiont (host) is neither harmed nor benefited
• satellitism, commensal intestinal bacteria (normal microbial
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flora)
3. ____________= parasite benefits, host is harmed
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Intestinal helminths, Rickettsia, all viruses
How microbes live
Non-symbiotic microbial associations
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organisms are free-living; relationships
not required for survival
• ____________– members cooperate and
share nutrients
• ____________– some members are inhibited
or destroyed by others
Ecological Associations Among Microorganisms
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Interrelationships Between Microbes and
Humans
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Human body is a rich habitat for symbiotic
bacteria, fungi, and a few protozoa normal microbial ____________
Commensal, parasitic, and synergistic
relationships
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Microbial Biofilms
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____________result when organisms attach to a
substrate by some form of extracellular matrix that
binds them together in complex organized layers
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Dominate the structure of most natural environments
on earth
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Communicate and cooperate in the formation and
function of biofilms – quorum sensing
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Figure 7.13
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How do microbes get their
nutrients??
What are the transport
mechanisms used to import
nutrients and export waste?
REMEMBER: Transport occurs across the
________________________…even in microbes
with cell walls, all that is going in or coming
out must cross the cell membrane
transport mechanisms
1.
____________– require no energy input
from cell (uses laws of physics, like
entropy)
2.
____________– require energy input from
cell
Transport mechanisms
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Passive transport –do not require energy,
substances exist in a gradient and move from
areas of higher concentration towards areas
of lower concentration
• ____________
• ____________– diffusion of water
• ________________________– requires a carrier
concentration
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Amount solute/solvent
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Solute can be solid, liquid, gas
Solvent is usually liquid
Percentage = ________________________
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Examples: 3% NaCl = 3 g in 100 mL = 0.3 g/L
Molarity = ________________________
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Examples: 1 M NaCl solution, 10 M glucose solution etc.
Tonicity: ____________> ____________in terms
of amount of solute. ____________means both
solutions have the same amount of solute.
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Examples:
10% NaCl is more hypertonic than 1% NaCl
1 M glucose is more hypotonic than 5 M glucose
diffusion
• Molecules move
along gradient:
• High  low
concentration
• Due to RANDOM
motion – increased
by heat (entropy)
• Evidence: Brownian
movement
Passive transport
Diffusion in cells
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Small, nonpolar molecules can diffuse across
cell membrane (oxygen, small lipids)
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Polar molecules – ____________
________________________ (facilitated
diffusion – still PASSIVE transport – using
energy of gradient)
Passive transport
Facilitated diffusion
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Carrier proteins embedded in membrane
Specific for a single type of molecule
Saturation can occur (all binding sites on
carrier proteins are occupied by molecule
being transported)
Competition – similar molecules can
compete for binding sites – one with
higher affinity (or concentration) will win
and be transported
Facilitated diffusion
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• ________________________
________________________
(therefore SOLUTE
cannot diffuse – so
water moves instead)
• WATER moves from
High  low water conc.
(essentially, water
moves from low
SOLUTE to high
SOLUTE)
• Water moves from
______________________________
______________________________
Passive transport
osmosis
Passive transport
Tonicity and osmosis
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____________– low solute (high water) –
has LOW osmotic potential (LOW osmotic
pressure). PURE WATER is the most
hypotonic
____________– high solute (low water) –
has HIGH osmotic potential (pressure).
Concentrated solutions (salt and sugar
preservatives) are highly hypertonic.
Passive transport
Adaptations to osmotic effects
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In a hypotonic environment:
Bacteria, algae have cell walls so they won’t
burst – they just become ____________.
Amoebas, ciliates have contractile vacuoles
constantly pumping water OUT
In a hypertonic environment:
Halobacteria actually absorb salt to try and
stay isotonic so they won’t LOSE water (ex.
Dead sea, Great Salt Lake)
Transport mechanisms
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____________transport – requires ____________
and carrier proteins, gradient ____________
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Examples: against gradient, faster than diffusion, large,
charged molecules that can’t go through membrane – all
require energy
• Carrier-mediated active transport (permeases/
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pumps)
Group translocation – transported molecule
chemically altered
• Bulk transport – ______________________
______________________________________
Carrier mediated active transport
Group translocation
See Na/K pump movie
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Bulk transport (________________) –
involves vacuole/vessicle formation
Active transport
Liquids,
solutions
apicomplexans
Large particles,
whole cells
Amoeba
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Active transport
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MICROBIAL GROWTH
Microbial growth
1.
Environmental influences on growth
2.
Biology – stages of growth
1. Environmental influences on microbial
growth
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temperature
oxygen requirements
pH
electromagnetic radiation
barometric pressure
Environmental influences
a. Temperature:
3 cardinal temperatures
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Minimum temperature – lowest
temperature that permits a microbe’s growth
and metabolism
Maximum temperature – highest
temperature that permits a microbe’s growth
and metabolism
____________temperature – promotes the
fastest rate of growth and metabolism
Environmental influences
3 temperature adaptation groups
1.
__________________– optimum
temperature below 15oC, capable of growth
at 0oC
2.
________________– optimum temperature
20o-40oC, most human pathogens
3.
________________– optimum temperature
greater than 45oC
3 temperature adaptation groups
Environmental influences
Thermus aquaticus
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DNA polymerase (known as Taq
polymerase) used in PCR (polymerase
chain reaction)
________________(1983) – Nobel Prize in
Chemistry - 1993
Enzyme is HEAT STABLE – so during
cycling of the PCR machine (95-55-77°C) it
does not get destroyed
Huge advance in biotechnology
Environmental influences
b. Oxygen requirements
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Depends on whether cell can handle
toxic byproducts (superoxide, peroxide)
________________________________
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Environmental influences
--Oxygen requirements
Aerobes vs. anaerobes
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______________– grown in normal O2,
can handle by-products. Some are
facultative anaerobes. Microaerophile –
cannot grow under anaerobic conditions,
but can handle some O2.
________________–
• strict – die in presence of O2.
• Aerotolerant – cannot perform aerobic
respiration, but are not killed by O2
Environmental influences
_____________________
broth – absorbs O2 from air
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Aerobic
(Pseudomonas)
Facultative anaerobe
(Staph aureus)
Facultative anaerobe
(E. coli)
Obligate anaerobe
(Clostridium)
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Anaerobic environmental
chamber
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Anaerobic jar – uses gas
packs that provide a
defined atmosphere
O2 removed from
atmosphere + H2 
water
Also used for
________________
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Environmental influences
c. pH, pressure and EM radiation
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pH – majority grow between 6-8
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Osmotic pressure – most are in hypotonic or
isotonic
• Acidophiles, Alkalinophiles
• Osmophiles/halophiles – grow in hypertonic (high
osmotic pressure); can cause food spoilage
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Hydrostatic pressure – barophiles (deep sea)
EM radiation – UV and ionizing rays are used in
microbial control. Damage DNA.
2. Biology of microbial growth
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a. Cell division – binary fission
b. Population growth rate
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c. Methods for analyzing growth
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• Generation/doubling time
• Growth curve – stages
of microbial growth
a. ______________________– dividingBiology
in two
Biology of microbial growth
b. Population growth rate: Exponential growth
Nf = total number of cells at
some point
Ni = starting number of cells
n = generation number
= elapsed time /
generation time (t/gen)
2n = number of cells in that
generation
b. Population growth curve
Shows growth progress
over a time period 
#cells/time
Steps:
1.Inoculate culture and
incubate
2.Sample (volume) at
time intervals
3.Plate onto solid media
4.Count number of cells
(get #cells/volume)
Biology of microbial growth
Biology of microbial growth
b. Stages of Growth curve
Biology of microbial growth
Growth curve
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2.
3.
4.
________ phase – “flat” period of adjustment,
enlargement; little growth
____________ growth phase – a period of maximum
growth will continue as long as cells have adequate
nutrients & a favorable environment
______________ phase – rate of cell growth equals
rate of cell death cause by depleted nutrients & O2,
excretion of organic acids & pollutants
___________ phase – as limiting factors intensify,
cells die exponentially in their own wastes
Biology of microbial growth
Importance of growth curve
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Antimicrobials – more effective on
exponential phase
Infectivity – early, middle stages – more
likely to pass microbe to others
Course of infection – fast growing
microbes can overwhelm host defenses
c. Methods for analyzing growth
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2.
Inoculate culture
Count cells
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________________– use spectrophotometer
________________
• Direct, total cell count (hemocytometer)
• Viable plate count (look at CFUs)
• Coulter counter/Flow cytometer
Biology of microbial growth
Turbidity
Biology of microbial growth
Enumeration - Direct microscopic count
Biology of microbial growth
Enumeration - Electronic counting